Paguristes nomurai, Komai & Asakura, 1995

Osawa, Masayuki & Fujita, Yoshihisa, 2019, Submarine cave hermit crabs (Crustacea: Decapoda: Anomura: Paguroidea) from three islands of the Ryukyu Islands, southwestern Japan, Zootaxa 4560 (3), pp. 463-482 : 472-473

Pagurixus nomurai Komai & Asakura, 1995

( Figs. 2C, D , 5A, B )

Pagurixus nomurai Komai & Asakura, 1995: 341 , figs. 1–3 (type locality: Kume Island, Ryukyu Islands).— Osawa & Takeda 2004: 1109.— Komai & Osawa 2006: 32, figs. 12–14, 44C, 47.— Poupin et al. 2013: 45, fig. 23D, E.— Osawa & Fujita 2016: 45, fig. 6B.— Tan et al. 2014: 411, fig. 12.

Material examined. Okinawa Island, Hedo Dome cave: main tube, 10 August 2016, 1 ovigerous female (sl 5.4 mm), RUMF-ZC-6034, ( HD 2016-51); main tube, 12 August 2016, 1 ovigerous female (sl 4.1 mm), RUMF-ZC- 6035 ( HD 2016-84); main tube, 30 m from entrance, area of rocks, 12 August 2016, 1 male (sl 4.5 mm), RUMF- ZC-6036 ( HD 2016-85); main tube, 13 August 2016, 2 males (sl 2.3, 4.5 mm), RUMF-ZC-6037 ( HD 2016-103, 104); main tube, 22 May 2017, 1 female (sl 5.0 mm), RUMF-ZC-6038 ( HD 2017-65); main tube, 21 May 2017, 1 male (sl 4.8 mm), 2 females (sl 3.7, 5.5 mm), RUMF-ZC-6039 ( HD 2017-85, 90). Shimoji Island , Akuma-no- Yakata cave: entrance, 1 September 2017 , 1 ovigerous female (sl 4.4 mm), RUMF-ZC-6040 ( SH 102).

Distribution. Widely distributed in the Indo-West Pacific: Mayotte, Réunion, Philippines, Taiwan, Japan, Guam, northwestern Australia, Samoa, Cook, and French Polynesia; subtidal to 60 m (Osawa & Chan 2010; Komai & Rahayu 2013; Poupin et al. 2013).

Habitat. Coral reefs; found among branches or plates of dead corals in moats or in submarine caves in forereef slopes ( Osawa & Takeda, 2004; Komai & Osawa 2006).

Remarks. In their redescription of P. nomurai, Komai & Osawa (2006, fig. 44C) noted that the fresh coloration of the pereopods is “generally brown, olive or bluish gray” and gave a photograph of bluish gray-colored specimen. Poupin et al. (2013, fig. 23D, E) and Arima (2014, unnumbered figs.) also showed similarly bluish graycolored specimens of P. nomurai . All the specimens have been recorded from rather open, coral and rocky reefs, although they usually hided in rubbles or crevices on the reefs. In the present specimens collected from submarine caves, the antennal flagella and pereopods are usually vivid reddish brown ( Fig. 2C ), whereas those of three ovigerous female specimens (sl 5.4 mm, RUMF-ZC-6034, HD 2016-51; sl 4.1 mm, RUMF-ZC-6035, HD 2016-84; sl 4.4 mm, RUMF-ZC-6040, SH102) are rather pale, light brown ( Fig. 2D ). The coloration of the ovigerous female (sl 4.4 mm, RUMF-ZC-6040, SH102) generally agrees well with that of a male reported by Osawa & Fujita (2016: fig. 6B); both specimens were collected from same locality, Akuma-no-Yakata cave in Shimoji Island. The “reddish brown” individuals were often observed by investigations in Hedo Dome cave. Tan et al. (2014: fig. 12) also gave a photograph of “reddish brown” specimen referred to P. nomurai from Thunderdome Cave in Christmas Island.

In comparison with the redescription of P. nomurai by Komai & Osawa (2006), the present specimens of the “reddish brown” and “pale light brown” morphs have proportionally more slender carpus of the left cheliped in general; 4.4–5.4 (reddish brown morph; Fig. 5A ) and 4.3–5.0 (pale light brown morph) versus 3.0–4.3 length of the width. Additionally, the chelipeds of the present specimens are less setose with shorter setae, particularly in females, than those of the Komai & Osawa’s (2006) material, although the authors cited the presence of relatively numerous tufts of stiff setae on the appendages is observed in large specimens, regardless of sex.

The differences in fresh coloration and elongation of the left cheliped of the present specimens could be attributed to the degree of adaptation for the dark habitat in submarine caves, although the morphometric range of the ambulatory legs in the present specimens agrees with that in the material of P. nomurai reported by Komai & Osawa (2006); for example on the propodi, 5.4–6.5 ( Fig. 5B ) versus 5.5–6.5 times longer than high. To determine as if these distinctions are interspecific variations and a cryptic species exists under the name P. nomurai , molecular data and more careful morphological comparison of the present specimens and other material referred to P. nomurai are needed and now in progress.

Figures

FIGURE 2. Entire animal, dorsal view. A, Catapagurus tuberculosus (Asakura, 1999), male (sl 4.9 mm), RUMF-ZC-6031 (IE188); B, Pagurixus longipes Osawa, Fujita & Okuno, 2006, male (sl 2.0 mm), RUMF-ZC-6033 (HD2017-133); C, Pagurixus nomurai Komai & Asakura, 1995, female (sl 5.0 mm), RUMF-ZC-6038 (HD2017-65); D, Pagurixus nomurai Komai & Asakura, 1995, ovigerous female (sl 4.4 mm), RUMF-ZC-6040 (SH102).

FIGURE 5. Pagurixus nomurai Komai & Asakura, 1995: female (sl 5.0 mm), RUMF-ZC-6038 (HD2017-65) (A, B); Pylopaguropsis granulata Asakura, 2000: female (sl 4.8 mm), RUMF-ZC-6052 (HD2017-31) (C–E); Pylopaguropsis keijii McLaughlin & Haig, 1989: male (sl 1.9 mm), RUMF-ZC-6055 (HD2017-87) (F). A, carpus of left cheliped, dorsal view; B, dactylus and propodus of left third pereopod, lateral view; C, right chela, dorsal view; D, carpus and merus of left second pereopod, lateral view; E, carpus and merus of left third pereopod, lateral view; F, propodus of right third pereopod, lateral view. Setae omitted from all illustrations. Scales equal 1.0 mm.